Osteopenia in extremely low birthweight infants

Daily physical activity in low-risk extremely low birth weight preterm infants: positive impact on bone mineral density and anthropometric measurements

The aim of this study was to evaluate the changes in bone mineral density and anthropometric indices of extremely low birth weight (ELBW) preterm infants undergoing daily physical activity. Twenty-eight low-risk ELBW preterm infants (intervention group = 14, control group = 14) with a birth weight of under 1000 g and gestational age of 26-32 weeks were recruited. Preterm infants in the control group were provided with standard nursing care, whereas those in the intervention group received a daily physical activity programme in addition to standard nursing care during the study. Before and after the study, anthropometric indices and tibial speed of sound (SOS) values were measured. In this study, the tibial SOS values were found to be increased in the intervention group (+111.14 m/s) (p = 0.001) and decreased in the control group (-58.21 m/s) (p = 0.030). The increase in percentage of body weight, height, and tibial length of infants in the intervention group was significantly higher than in the control group (respectively; p = 0.002, p = 0,015, p < 0.001). A daily physical activity programme increased body weight, height, tibial length, and SOS values of the tibia in ELBW preterm infants.

High incidence of rickets in extremely low birth weight infants with severe parenteral nutrition-associated cholestasis and bronchopulmonary dysplasia

Risk factors for rickets of prematurity have not been re-examined since introduction of high mineral formula, particularly in ELBW infants. We analyzed the incidence and the risk factors of rickets in extremely low birth weight (ELBW) infants. As a retrospective case-control study from 2004 to 2008, risk factors were analyzed in 24 patients with rickets versus 31 patients without. The frequency of rickets in ELBW infants was 24/55 (44%). Infants with rickets were diagnosed at 48.2 ± 16.1 days of age, and improved by 85.3 ± 25.3 days. By radiologic evaluation, 29% were grade 1 rickets, 58% grade 2 and 13% grade 3. In univariate analysis, infants with rickets had significantly higher incidence of patent ductus arteriosus, parenteral nutrition associated cholestasis (PNAC), severe PNAC and moderate/severe bronchopulmonary dysplasia (BPD). In multiple regression analysis, after adjustment for gestation and birth weight, rickets significantly correlated with severe PNAC and with moderate/severe BPD. Serum peak alkaline phosphatase levels were significantly elevated in rickets (P < 0.001). In ELBW infants, the incidence of rickets of prematurity remains high and the incidence of severe PNAC and moderate/severe BPD was significantly increased 18 and 3 times, respectively.

Osteopenia of prematurity: a national survey and review of practice

Premature infants are at significant risk of reduced bone mineral content (BMC) and subsequent osteopenia. There are currently no standard practices regarding screening, investigation or treatment of this condition. We present a case report and findings of a national survey of 36 level 2 and 3 neonatal units (72% response rate). The findings showed widely disparate practice regarding screening, prevention and treatment. We summarize the tests currently available for osteopenia and suggest guidelines for management of the at risk group.

CONCLUSION

Our survey confirms inconsistent practices regarding management of infants at risk of osteopenia of prematurity. Investigations and treatments available are summarized together with a guideline for management of this susceptible group of infants.

The role of cord blood IGF-I levels in preterm osteopenia

OBJECTIVE

Osteopenia is a frequent condition in preterm infants. This prospective study was designed to assess the relationship between cord blood insulin-like growth factor-I (IGF-I) levels and bone mineralization in healthy premature infants.

METHODS

Twenty preterm infants (ten males and ten females) were studied. We determined the bone mineral density (BMD) and bone mineral content (BMC) of healthy premature infants by dual-energy X-ray absorptiometry and also studied the correlation between IGF-I and other parameters and the influence of cord blood IGF-I concentrations on bone mineralization in these infants.

RESULTS

The mean concentration of IGF-I was 13.6 +/- 16.9 ng/ml and BMD and BMC were 0.249 +/- 0.06 g/cm2 and 3.09 +/- 1.18 g, respectively. Cord serum levels of IGF-I had significantly positive correlations with BMD (r = 0.605, p = 0.008), but not BMC (r = 0.242, p = 0.367). In stepwise regression analysis, IGF-I emerged as a significant predictor of BMD (beta = 0.595, p = 0.015) contributing to 35.4% of its variability.

CONCLUSION

We found a relationship between cord blood IGF-I and BMD in preterm neonates, suggesting that even within an unremarkable population, IGF-I might be important to ensuring bone health.

Nutrition for preterm infants after hospital discharge

Preterm infants accrue significant nutrient deficits during hospitalization, and at the time of discharge most VLBW preterm infants have moderate to severe growth failure. Infants with significant morbidities and infants with ELBW have more severe growth failure since they regain birth weight at a later age, and they gain weight more slowly. Catch-up growth accelerates after hospital discharge. The rates of catch-up growth vary according to many factors including birth weight, gestational age, parental size, adequacy of intrauterine growth, neurologic impairment, clinical course, and nutrition. Most catch-up growth occurs within the first 2 to 3 years of life; however, compensatory catch-up growth may continue into adolescence and adulthood. Despite evidence of ongoing catch-up growth, the mean growth measurements of children and adults who were born preterm and with VLBW are lower than their term-born peers. Accelerated rates of catch-up growth are associated with better neurodevelopmental outcomes. Inadequate head circumference growth, in particular, may have long-term prognostic significance for later neurodevelopment in preterm infants. Nutrient-enriched formulas that provide 22 kcal/oz are often prescribed for VLBW preterm infants after hospital discharge. Several studies have reported that preterm infants fed the enriched versus standard term infant formulas have greater rates of catch-up growth during the first year of life, including greater increases in head circumference. The nutrient-enriched formulas appear to be of particular benefit for male infants. There is less information regarding the nutrient needs of breast-fed infants after hospital discharge. However, several studies have demonstrated that preterm infants fed unfortified human milk after discharge have growth rates and bone mass that are lower than formula-fed infants during infancy. The use of fortified human milk, or alternate feedings with a nutrient-enriched formula may be useful for breast-fed infants who have delays in catch-up growth. Additional studies are needed to determine whether enriched feedings might be of particular benefit for preterm infants who are at greater risk for postnatal growth failure, including infants born SGA, or with extremely low birth weights, intrauterine growth restriction, or chronic conditions such as bronchopulmonary dysplasia. The potential effect of nutritional programming on long-term outcomes of preterm infants also requires further investigation.

Bone mineralization and growth are enhanced in preterm infants fed an isocaloric, nutrient-enriched preterm formula through term

BACKGROUND

Because recent data on the effects of mineral concentrations in preterm infant formula on bone mineralization are lacking, recommendations for the mineral content of preterm infant formula differ greatly between committees.

OBJECTIVE

The goal of the study was to assess the effects of an isocaloric, nutrient-enriched preterm formula, which was fed from the age when full enteral feedings were tolerated through expected term, on bone mineralization in preterm infants.

DESIGN

We conducted a prospective, randomized, double-blind study in healthy, preterm infants (gestational age of 28-32 wk) who were fed either a control preterm formula (n=20) or an isocaloric, nutrient-enriched preterm formula (n=21) until 3 mo of age (ie, approximate expected term). Serum calcium indexes were taken throughout the study, and bone mass was determined by using dual-energy X-ray absorptiometry at hospital discharge and expected term.

RESULTS

A total of 37 infants (experimental formula, n=19; control formula, n=18) completed the study. Compared with control subjects, infants fed the experimental formula had 25% and 40% higher intakes of calcium and phosphorus, respectively. Serum calcium, phosphorus, osteocalcin, and alkaline phosphatase concentrations and urinary collagen type I cross-linked N-telopetide concentrations were not significantly different between the groups at any time point. The bone mineral content of infants fed the experimental formula was 23% (P=0.039) and 35% (P=0.002) higher at hospital discharge and expected term, respectively.

CONCLUSIONS

Bone mineralization at hospital discharge and expected term was significantly higher in preterm infants fed the isocaloric, nutrient-enriched formula than in those fed control formula. Continuation of the experimental formula beyond hospital discharge, through expected term, further improved bone mineralization.

Pre- and post-discharge feeding of very preterm infants: impact on growth and bone mineralization

In this prospective study we examined (1) how the nutritional status of very preterm infants, judged by growth measures and biochemical values, evolved during the initial hospitalization; (2) the effect of feeding on growth after discharge from hospital; and (3) the risk factors associated with low lumbar bone mineral content (BMC) later in infancy. Sixty-four former preterm infants had their lumbar spine (L2-L4) BMC assessed by dual energy X-ray absorptiometry when they weighed between 5 and 7 kg. Predicted BMC values were calculated based on our previously reported reference lumbar BMC data. These values were used to convert the preterm infants' BMC values into percentages. The extremely preterm group (gestational age < or =28 weeks) had significantly more respiratory morbidity and longer duration of hospital stay than the more mature infants. Both groups developed growth retardation and malnutrition during the hospital stay. Exclusive breastfeeding after discharge from hospital supported linear catch-up growth and weight gain but was associated with a 7.0 (1.2-41.7)-fold risk of having low BMC values. The other factors associated with the risk of having low BMC values later in infancy were low serum phosphate levels at 6 weeks, with a 7.8 (1.6-37.0)-fold risk, and male gender, with a 4.3 (1.2-16.1)-fold risk. Appropriately designed interventional studies are needed to improve the growth and nutrition of these infants during initial hospitalization. In order to improve the postdischarge nutrition, we suggest that the amount and duration of multicomponent human milk fortification should be studied further to provide individualized nutrition throughout the catch-up growth period until the end of the first year of life.

Bone mineralisation in premature infants cannot be predicted from serum alkaline phosphatase or serum phosphate

BACKGROUND

The bone mineral content of premature infants at term is lower than in mature infants at the same postconceptional age. Serum alkaline phosphatase and serum phosphate are often used as indicators of bone mineralisation.

OBJECTIVE

To analyse the association between bone mineral content and serum alkaline phosphatase and serum phosphate.

METHODS

Serum alkaline phosphatase and phosphate were measured at weekly intervals during admission in 108 premature infants of gestational age below 32 weeks (mean (SD) gestational age 29 (2) weeks; mean (SD) birth weight 1129 (279) g). Bone mineral content was measured at term (mean gestational age 41 weeks) by dual energy x ray absorptiometry and corrected for body size.

RESULTS

Serum alkaline phosphatase was significantly negatively associated with serum phosphate (p < 0.001). Bone mineral content was not associated with mean serum alkaline phosphatase (p = 0.8), peak serum alkaline phosphatase (p = 0.5), or mean serum phosphate (p = 0.2) at term.

CONCLUSION

Routine measurements of serum alkaline phosphatase and serum phosphate are of no use in predicting bone mineralisation outcome in premature infants.

Bone mineral metabolism in the micropremie

Environmental factors, nutritional supplies, hormonal status, diseases, and treatments appear to affect postnatal skeletal growth and mineralization in VLBW infants. Compared with their term counterparts, ELBW infants are at risk of postnatal growth deficiency and osteopenia at the time of hospital discharge. From recent data, DXA is becoming one of the reference techniques to evaluate mineral status, whole-body composition, and effects of dietary manipulations on weight gain composition and mineral accretion in preterm infants. Weight gain and length increases need to be evaluated carefully during the first weeks of life, in the intensive care unit and out of it, in the step down unit. Nutritional survey is required to improve the nutritional supply and to maximize linear growth. As the critical epoch of growth extends, during the first weeks or months after discharge, follow-up and nutritional support need to be provided during the first years to promote early catch-up growth and mineralization. Further studies need to determine precisely the most optimal feeding regimen during this period but also need to evaluate the long-term implications of such a policy on stature, peak bone mass, and general health at adulthood.

Diet and bone mineral content at term in premature infants

Premature infants are at risk of developing metabolic bone disease mainly because of low calcium and phosphorus intake. We have examined the effect of different mineral supplements on bone mineral content at term in 127 premature infants with gestational age <32 wk in a double-blinded randomized trial. We used either phosphate supplementation of human milk as recommended by the European Society of Pediatric Gastroenterology and Nutrition or fortified supplementation with protein, calcium, and phosphorus or preterm formula as recommended by the American Academy of Pediatrics. The intervention period was from 1 week old until 36 wk of gestational age, and the infants were fed approximately 200 mL x kg(-1) x d(-1). Bone mineral content was measured at term by dual-energy x-ray absorptiometry scan. Surprisingly, neither phosphate, fortifier, nor preterm formula supplementation had any significant effect on bone mineral content at term compared with infants fed their own mother's milk only. There was a tendency to higher total bone mineral content in infants fed preterm formula compared with infants fed their own mother's milk only (p = 0.05), but when the bone mineral content was corrected for the size of the infant, there was no difference (p = 0.68). Infants fed preterm formula had a significantly higher weight at term compared with infants fed their own mother's milk only (p = 0.02), but did not differ significantly in length or head circumference. In a regression analysis, the amount of supplemented phosphorus was significantly associated with weight at term (p = 0.008). We conclude that when feeding 200 mL x kg(-1) x d(-1), mineral supplementation of human milk or use of preterm formula does not significantly improve bone mineralization outcome at term.

Bone mineralization in preterm infants

In preterm neonates a large skeletal mineral deficit builds up between birth and 40 wk postconception. During the phase of catch-up growth between 40 and 60 wk postconception there is a catch-up in peripheral skeletal mineralization, so that by the age of 1 y the skeletal mineral content is similar in preterm and term infants, despite the former being smaller, a finding that has been replicated for lumbar spinal mineralization. Later follow-up studies suggest that this catch-up persists and mineralization remains appropriate for body size. However, given the continuing abnormal growth experience of former preterm individuals, it would still be important to examine their bone mineralization in early adulthood. A number of interventions can improve perinatal bone mineralization, but few studies examine their long-term effectiveness. One such study has suggested that a relatively poor mineral diet in this period is, counterintuitively, associated with a later advantage in skeletal mineralization. If this finding is repeatable, then it could result in a major change in nutrition strategy in the neonatal period.

Spontaneous resolution of bone mineral depletion in preterm infants

Fifteen preterm infants and 17 born at full term whose gestational ages ranged from 25 to 34 weeks and 38 to 42 weeks, respectively, were examined initially at postconceptional ages ranging from 38 to 44 weeks and subsequently at 46 to 71 weeks. Each examination included measurement of bone mineral content of the mid-forearm by single photon absorptiometry. For the preterm group, the mean (SD) value of bone mineral content at the first examination was 109.0 (27.6) mg/cm and was significantly lower than the corresponding value of 194.4 (19.6) mg/cm for the whole full term group. The mean subsequent rate of mineral accretion in the preterm group was 8.70 (4.60) mg/cm/week, the mean individual duration of observation being 9.7 weeks. Rate of mineral accretion for the full term group was independent of the duration of observation and averaged 1.60 (2.20) mg/cm/week. The difference between mean values of rate of mineral accretion in the preterm and full term groups was highly significant. Our results show that there is a phase of rapid mineral accretion starting at 40 weeks' postconception in preterm infants that substantially reduces the perinatal mineralisation deficit.

Bone mineral content and body size 65 to 100 weeks' postconception in preterm and full term infants

A total of 36 preterm and 22 full term infants were weighed and measured at 65 to 100 weeks' postconception. It was found that the preterm infants were on average significantly lighter by 1008 g and shorter by 3.8 cm than those born at full term. Despite the smaller size of preterm infants, mean values of bone mineral content in the mid-forearm were not significantly different between the two groups. In contrast, near 40 weeks' postconception the mean bone mineral content observed in 35 of the preterm infants was significantly smaller than that observed in eight of the full term infants. Our results suggest that there is a phase of rapid mineral accretion between 40 and 60 weeks' postconception. This 'catch up' in mineral accretion reduces the perinatal mineralisation deficit that might otherwise persist into childhood.

Bone mineral accretion rate and calcium intake in preterm infants

Thirty six preterm infants (20 boys) of 25 to 32 weeks' gestation were observed from birth to around 40 weeks' postconception. When oral feeding became possible, nine received mother's own breast milk (group B), 15 formula feed (group F), and 12 formula feed supplemented with calcium (5 ml 10% calcium gluconate/100 ml feed) and phosphorus (0.5 ml 17% potassium phosphate similarly) (group S). All received a daily supplement of 400 IU vitamin D. Intakes of calcium, phosphorus, vitamin D, energy, and fluid volume were recorded. When oral feeding started, and near 40 weeks' postconception, bone mineral content of the forearm was measured by photon absorptiometry; weight and crown-heel length were also measured. After logarithmic transformation of the measurements, there were no significant intergroup differences between the mean rate constants for weight or crown-heel length describing growth during the observation period. The mean rate constant for mineral accretion (M) was significantly higher in group S than in both the others. Pooling all data, M was significantly correlated with calcium intake but not with any other variable. Mineral supplementation of feed can reduce but not cure osteopenia of prematurity.